Thermorelay element



Sept. 2, 1952 1. s. BLONDER THERMORELAY ELEMENT Fi led June 12, 1951 STATION INVENTOR. Isaac 6. Blonder BY A 1 fiwwm Patented Sept. 2, 1952 UNITED, STATES PATENT OFFICE 7 Claims. (Cl. 20071 13) The present invention relates to thermo-relay elements and more particularly to bi-metallic thermo-relay elements.

An object of the present invention is to provide a new and improved thermo-relay element Thermo-relay elements have heretofore been constructed of adjacent layers of bi-metal materials in order to bend in response to temperature variations, such as those caused by the passage of electric current through the element, either in the direction of one of the bi-metal layers, or in the direction of the other layer, depending upon the different temperature coefficients of expansion of the layers. Such devices have been utilized for the opening or closing of electric circuits and similar apparatus. Among the difilculties attendant e se such rm relay elements is the unstable performance of the elements when varying temperature effects are-produced in the medium surrounding the elements. If, for example, a thermo-relay element is placed in an electric apparatus where there are vacuum tubes or other electrical components that generate heat into the surrounding air, non-uniform, varying temperature gradients are set up in the air surrounding the thermorelay element. Whereas the bi-metal thermorelay element may have initially been adjusted to close a pair of contacts spaced a predetermined distance apart in response to a particular threshold value of current in the element, these external temperature gradients will alter the intended performance of the element. Various temperature-compensating. devices have heretofore been proposed to overcome this difficulty,

such as temperature-controlled chambers or temperature-compensating bi-metal arms, but these add materially to the cost and/or size of the thermo-relay element.

Still an additional object ofthe present invention is to provide an extremely simple and inexpensive thermo-relay element that is not subject to the above-mentioned difficulties and that automatically is self-compensatory to ambient temperature changes in allv planes with respect to the thermo-relay element.

A further object is to provide a thermo-relay element that takes up very little spaee, that is light and compact, and that is extremely simple to manufacture.

Other and further objects will be explained hereinafter and will be more particularly pointed out in the appended claims. I

In summary, the present invention -relates to a bi-metal thermo-relay element having a base and two bimetal arms and an intermediately disposed bimetal tongue extending from the base. For best results, the width of the tongue is pref erably greater than the width of each of the arms. The free ends of the arms are each pro vided withsecuring means for securing the relay at two points to permit the arms to bend about the two points in response to temperature variations in the element. The tongue is free to move at its free end and is there provided witha contact member, the tongue moving in a direction opposite to the direction of bend of the arms, in order to move the contact member in the opposite direction to the bending movement of the arms. A cooperating contact member is engaged by the tongue "contact member to close a desired relay-operated circuit. Preferred constructional arrangements are hereinafter discussed in detail.

The invention Will now be described in' connection with the accompanying drawing Fig. 1 of which is a perspective view of a thermo- -r'elay element constructed in accordance with the present invention, shown embodied in a typical electric circuit, and Figs. 2 and 3 are side elevations of the relay in different positions of operaformed from a flat planar sheet of superposed layers of bi-metal material the upper surface l of which may, for example, be constituted of sheet steel, and the bottom surface 5, of sheet brass. Other Well known relay materials may, of course, also be employed. The relay comprises a substantially U-shaped member having a pair of co-planar,"substantially parallel arm's II connected at one end by the neck of the U a preferably right-angularly oriented connecting portion or base E3. The arms ll may be secured at their open ends to two points on the upper surface ofa'preferab1y planar insulating support I, as of Bakelite, by two pairs of eyelets 9. The left-hand pair of eyelets 9 serves asa pair of electric terminals for connection, respectively, with conductors 2,5 and 22', conneoting'one side of a source of energy 2, such'as the alternatingecurrent mains, to an electric system to be energized, shown as a' master station ll. The master station 4 may, as an illustration, be a television receiver that is energized from' the source 2 through the conductor. 25, the seriesconnected relay patheomprising the left-hand arm I 1, Fig. lythebase sand the right-hand metal material, is connected to the base I3 midway between the arms I I, and extends therefrom between and preferably substantially in the plane of the pair of arms II toward their open ends.

As the current from the source 2 flows'through I the arms II bending them upward aboutthe previously described axis A of the insulating support I, the tongue I5 is bent in the opposite direction, shown as downward in Fig. 3, about an axis B along the base I3, preferably disposed substantially parallel with the axis A. As the tongue I5 bends downward, a contact I7, such as asilver rivet mounted near its'free end, is moved into electrical engagement with a further cooperating contact I2 carried at the end of a resilient tongue support I4 between, though below the plane of, the arms II. To this end, the tongue support I4 is secured by an eyelet It to the lower surface of the insulating support I. This permits current flowing from the source 2 through the conductor 25 and the left-hand arm II to pass along the tongue I5 and through the connected contacts I1 and I2 to the eyelet Ill. The eyelet IE3 may serve as an electric terminal for afurther conductor 33 connected with a further electric system shown as a slave station 5. The conductor 293Il completes the connection of the source 2 to the slave station 6. The slave station 6, as an example, may be a television booster or pre-amplifier that it is desired to energize a predetermined interval of time, depending upon the speed of operation of the relay, after the master station television receiver 4 is energized. The relay operation may vary from substantially instantaneous closure of the contacts I! and I2 to a few secondsdelay before closure, as an illustration, depending upon the value of current passed through the relay, the relay dimensions and the initial spacing of the contacts I! and I2. This initial spacing may be conveniently varied by means of a screw is threaded from the upper to the lower'surface'of the insulating support I andbearing upon the tongue support I4 at a point displaced from the eyelet I0, thereby controlling the adjustment of the distance between the contacts I1 and I2.

In order to prevent the tongue I5 from heating as much as the arms II, thereby to insure that it does not reach such a high temperature that it tends to curl or bend upward in the same direction as the arms II, destroying the contact between the tongue contact member I! and the contact member I2, the tongue I5 is made wider than the arms II. As an illustration, the tongue I5 may be two or threetimes as wide as each arm I I. The current passing through the tongue I5 is thus distributed along a surface twoor three times greater than the surface of the arms II, insuring that the tongue does not heat'as much as the arms. Furthermore, since the lefthand arm II passes additional current not also passed along the right-hand arm II, in the circuit comprising the left-hand arm II and the tongue l5, the tongue I5 should be wider than the arm II in order to insure that its tendency to curl upward in response to the current passed therethrough shall be less than that of the lefthand arm II, thereby causing the tongue contact member I! to exert greater pressure upon the contact member I2.

The relay construction of the present invention is entirely self-compensatory for variations in the temperature of the medium surrounding the relay. Considering, first, temperature changes in planes of the medium normal to the plane of the arms II and the tongue I5, whatever temperature variations may occur, these variations act both upon the arms II and the tongue I5; and

because the lengths are substantially the same,

they produce substantially the same cumulative effect upon the arms II and the tongue l5. The bending a'ctionof the arms II about the axis A and the oppositely directioned bending action of the tongue I5 about the axis B, therefore, are equally affected by the temperature changes so that the relay will efiect closure of the contacts I! and I2 in response to substantially precisely the same threshold'value of current from the source 2 irrespective of such ambient temperature fluctuations. As for variations in the temperature gradient of the medium in the plane of the arms II and the tongue I5, since the arms II straddle the tongue I5, the cumulative effect therein is substantially the same as the effect upon the intermediate" tongue I5. Such temperature variations, therefore, also do not afiect the reliable and-reproducible operation of the relay. q

A typical bi-metal relay of sheet brass and sheet steel, or other bi-metallic combinations known to the art for use as temperature sensitive devices, a few thousandths of aninch thick, for operation with conventional alternating-current 1l0-volt mains may have the following dimensions. The arms II-may be about an inch long between their end-connecting or base portion 13 and the axis A of the insulating support I; the tongue I5, just under an inch in length-in order just to clear the edge of'the support I at the axis A; thejwi'olth of the arms II, about one sixteenth of an inch; the width of the tongue I5, about three sixteenths of an inch, spaced at each edge about one sixteenth of an inch from the adjacent arms II; and the width of'the connecting or base portion I3, about three'sixteenths of an inch. The spacing between the contacts II'and I2 may be of the order'ofa sixteenth of aninch.

While the. relayiof the present invention has been described as applied tomaster-slave electric circuits, it is to be understood that it is equally applicable to any circuit requiring a currentor temperature-controlled relay, such as plate-voltage relays in vacuum-tube circuits or automobile left-right indicator circuits, to mention but a few. The invention finds particular application. where light weight, limited space and low cost are important factors, and where temperature-compensating features are required. Though the U-shaped relay is shown provided with a rectangular contour, it may be of somewhat different shape, such as of semicircular contour, though the rectangular configuration has the advantages of easy and reliable die-stamping and the provision of a bending axis B disposed substantially parallel to the axis A for producing 'optimum bending leverage for the tongue.

Further modificationswill occur to those skilled in the art and all such are considered to fall within the spirit and scope of the present invention as. defined in the. appended claims.

What is claimed is 1. A thermal relay, having a base and two bi-i metal arms and an intermediately disposed bimetal tongue extending from the base, the width of the tongue being about two to three times the width of each of the arms, an insulating support to two points of which are secured, along an edge thereof, the free ends of the arms to permit the arms to bend about the edge away from the supportin response to temperature variations, the securing means being provided with electricterminals forjco'nnecting the arms in seriescircuit with a source of energy to effect the said temperature variations in the relay, and the tonguehaving a contact member at its free end and being free to move at -its free end past the said edge in order that the tongue may move in a direction opposite to the direction of bend of the arms, a further'contact member disposed between the said two points for cooperating with the tongue contact member, and electrical terminal means connected with the further contact member for connecting one of the arms and the tongue in series circuit with the source of energy when the tongue contact member and the further contact member are in engagement.

2. A thermal relay having a base and two bimetal arms and an intermediately disposed bimetal tongue extending from the base, an insulating support, means for securing the free ends of the arms at two points on one surface of the support,;along an edge thereof, in order to permit the arms to bend about the edge away from the support in response to temperature variations in the relay, the securing means being provided with electric terminals for connecting the arms in series circuit with a source of energy to effect the said temperature variations in the relay, the tongue having a contact member at its free end and being free to move at its free end in order that the tongue may move in a direction opposite to the direction of bend of the arms, a further contact member supported upon the oppositely disposed surface of the insulating support between though out of the plane of the arms for cooperating with the tongue contact member, and electric terminal means connected with the further contact member for connecting one of the arms and the tongue in series circuit with the source of energy when the tongue contact member and the further contact member are in engagement.

3. A thermal relay having a base and two bimetal arms and an intermediately disposed bimetal tongue extending from the base, a planar insulating support, means for securing the free ends of the arms upon one surface of the insulating support, along an edge thereof, to permit the arms to bend about the edge away from the said one surface of the support in response to temperature variations in the relay, the securing means being provided with electric terminals for connecting the arms in series circuit with a source of energy to effect the said temperature variations in the relay, the tongue having a contact member at its free end and being free to move at its free end in order that the tongue may move in a direction opposite to the direction of bend of the arms, a further contact member supported upon the oppositely disposed surface of the planar support between though out of the plane of the arms for cooperating with the tongue contact member, means for varying the distance between the contact members, and electric, terminal means connected'with the further contact member for connecting one of the arms and the tongue in series circuit with the source of energy when the tongue contact member and the further contact member are in engagement.

4. A thermal relay having a base and two bimetal arms of substantially equal length and an intermediately disposed bimetal tongue extending'from thev base, a planar insulating support, means for securing the free ends of the arms upon one surface of the insulating support, along an edge thereof, to permitv the arms. to bend about the edg'e'awayfrom the said one, surface ofthe'support in response to temperature variations in the relay, the securing means being provided with electric terminals for connecting the arms in series circuit with a source of energy to effect the said temperature variations in the relay, the tongue having a contact member at its free end and being free to move at its free endv in order that the tongue may move in a directionopposite to the direction of bend of the arms, a further contact member, a support for supporting the further contact member upon the oppositely disposed surface of the planar supportbetween though out of the plane of the arms for cooperating with the tongue contact member, means comprising anadjustable screw threaded through the planar support for bear ing upon the"further-contact-member support in order to vary the distance between the contact members, and, electric terminal means connected with the further contact member for connecting one of the arms and the tongue in series circuit with the source of energy when the tongue contact member and the further contact member are in engagement.

5. A thermal relay having a base and two coplanar bimetal arms constructed of superposed planar strips of different metals of substantially equal length and an intermediately disposed planar bimetal tongue of the same bimetal construction extending from the base, a planar insulating support, means for securing the free ends of the arms upon one surface of the insulating support, along an edge thereof, to permit the arms to bend about the edge of the support out of the plane of the support in response to temperature variations in the relay, the securing means being provided with electric terminals for connecting the arms in series circuit with a source of energy to effect the said temperature variations in the relay, the tongue having a contact member at its free end and being free to move at its free end in order that the tongue may move along an axis substantially parallel to the said edge of the support in a direction opposite to the direction of bend of the arms, a further contact member, means comprising a further tongue carried upon the oppositely disposed surface of the insulating support for supporting the further contact member between though out of the plane of the arms for cooperating with the bimetal tongue contact member, and electric terminal means connected with the further tongue for connecting one of the arms and the bimetal tongue in series circuit with the source of energy when the bimetal tongue contact member and the further contact member are in engagement.

6. A thermal relay having a base and two coplanar bimetal arms constructed of superposed planar strips of different metals of substantially equal length and an intermediately disposed planar bimetal tongue ofthe same bimetal construction extending from the base, the width of the tongue being greater than the width of each of the arms, means for securing the free ends of the arms upon one surface of the insulating support, along an edge thereof, to permit the arms to bend about the edge of the support out of the plane of the support in response to temperature variations in the relay, the securing means being provided with electric terminals for connecting the arms in series circuit with a source of energy to effect the said temperature variations in the relay, the tongue being free to move at its free end in order that the tongue may move along an axis substantially parallel to the said edge of the support in a direction opposite to the direction of bend of the arms, a further contact member, means comprising a further tongue carried upon the oppositely disposed surface of the insulating support for supporting the further contact member between though out of the plane of the arms for cooperating with the bimetal tongue contact mem ber, means for varying the position of the further-contact-member supporting means from the said oppositely disposed surface of the insulating support in order to vary the distance between the contact members, and electric terminal means connected with the further tongue for connecting one of the arms and the bimetal tongue in series circuit with the source of energy when the bimetal tongue contact member and the further contact member are in engagement.

7. A thermal relay having a base and a bimetal arm and a bimetal tongue extending from the base, "the width of the tongue being greater than the width of the arm, the free end of the arm being provided with securing means for securing the relay at a point to permit the arm to bend about the point in response to temperature variations, means connected to the securing means for initially passing current from a source of energy through the arm but not through the tongue in order to effect the said temperature variations in the arm, the tongue having a contact member at its free end and being free to move at its free end in order that the tongue may move in a direction opposite to the direction of bend of the arm, a further contact member disposed near the said point for cooperating with the tongue contact member and electric terminal means connected with the further contact member for connecting the arm and the tongue in series circuit with the source of energy when the tongue contact member and the further contact member are in engagement.

ISAAC S. BLONDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,997,011 ODonovan Apr. 9, 1935 2,126,981 Van Dyke Aug. 16, 1938 2,171,895 Sardeson Sept. 5, 1939 2,284,383 Elmer May 26, 1942 2,302,399 Stimson Nov. 17, 1942 2,518,361 Mosley Aug. 8, 1950 2,578,947 Rothwell et al Dec. 18, 1951 

